One of the less-known but often used in batch files features of COPY is the ability to substitute names and extensions.
This allows us to do
copy .bat .bak
to make a backup of all batch files, or
copy database. dbcopy.
to make a copy of all the database files.
Alas, dosbox doesn't implement this feature and this breaks some scripts. Attached patch implements it cleanly and solves the problem.
(It is against the 0.72, but I hope it isn't much of a problem.)